"Semantic" actually means something important in the context of HTML, and this project completely violates it.
Semantic UI has a meaning. The authors chose to ignore its meaning while trading on the cachet of the name. While their web dev skills may be unsurpassed, it's a reasonable criteria on which to judge them.
A single post or two on the name I could understand, but every comment? HN fixates on the absurd.
Calling something Semantic UI and comparing it to another library, that more follows the actually meaning of semantic, is silly. Yes you can change the class name but setting up the name as something meaningful, something semantic, such as 'submitButton' lets you redefine it in the CSS.
If I'm building something that multiple clients will use I don't want each client having buttons with class names specific to the client, but something I can modify easily in the CSS to get the look and feel they want.
It's ass backwards.